The blend of crude oil in a pipeline that ruptured last week in Arkansas didn’t come from oil-sands deposits in Canada, despite a Maine environmental group’s claims, the head of the New England Petroleum Council said Wednesday.

“The incident in Arkansas involves Wabasca Heavy, a conventionally produced heavy crude from western Canada,” said John Quinn. “Claims that the spilled crude is derived from Alberta bitumen oil sands are not true.”

Quinn was responding to a media release from Environment Maine, which drew a connection between the spill of 12,000 barrels of oil from ExxonMobil’s Pegasus pipeline and its cargo of “dirty tar sands oil.”

The spill forced the evacuation of 22 homes. It is still being cleaned up and the cause is being investigated by state and federal agencies.

The incident is adding a level of complexity to the debate over further development of the massive, bitumen-soaked sand deposits in western Canada. At issue is the definition of “tar-sands” oil, how it’s extracted and its chemical properties.

The Pegasus spill triggered a quick reaction from activists who are fighting pipeline projects meant to move oil from western Canada. They say the oil is more corrosive and more likely to damage pipelines. In Maine, there’s vocal opposition to potential plans for the Portland pipeline to reverse its flow from west to east and move Canadian oil from Montreal to South Portland.

“This accident … is also a glimpse into the very real consequences we could face in Maine if the Portland-Montreal pipeline is allowed to carry the same dirty tar sands oil through our state,” said Emily Figdor, Environment Maine’s director.

TransCanada, the giant Canadian energy company, announced Tuesday that it intends to develop a pipeline more than 2,500 miles long to bring as much as 850,000 barrels of oil a day from Alberta to refineries in Quebec and Saint John, New Brunswick. That line, which could be in operation by 2017, would likely skirt northern Maine. It’s an example of the market forces behind the rush to expand development of Canada’s western oil deposits for global and domestic refineries.

The continent’s network of petroleum pipelines moves billions of gallons of oil every year. But recent high-profile spills, and environmentalists’ concerns that burning western Canada’s bitumen deposits is speeding up climate change, has drawn attention to the specific kind of oil moving in the pipelines.

In the Pegasus spill, ExxonMobil has identified the product as Wabasca Heavy, a blend of heavy oil from the Athabasca region of Alberta, according to CrudeMonitor, which analyzes Canadian oil.

The oil is driven out of the ground by injecting polymers and water, to raise the viscosity and make the thick oil flow easier. According to ExxonMobil and the New England Petroleum Council, the blend is considered conventional heavy oil.

But to environmental groups, the industry’s distinction is a matter of semantics.

In a blog post Tuesday, the Natural Resources Defense Council noted that Wabasca Heavy comes from the regional identified by Alberta’s government as containing oil sands. And the process of injecting polymer solvents is little different from injecting steam, a common method to extract tar sands.

Environmental groups say the chemical composition and sediments in tar-sands oil increase the risk of corroding pipelines and causing spills.

The industry disputes that. And the basic analysis of Wabasca Heavy by Crude Monitor doesn’t indicate a higher risk of pipeline corrosion or damage, according to Larry Wilson, president of Portland Pipe Line Corp.

Wilson was asked to comment on the basic chemical makeup and properties of routine samples of Wabasca Heavy taken by Crude Monitor over a five-year period. They cover properties including density, sulphur content and sediment.

In terms of sediment, the Wabasca samples contained concentrations that were a small fraction of what the Portland pipeline sets for a maximum level. “This is not dirty crude that wears out a pipeline from the inside,” Wilson said.

Portland Pipe Line moves heavy crude from around the world, testing each load to make sure it complies with the design of the pipeline and its equipment. Wilson said he’s waiting to hear the cause of Pegasus spill but he doubts it has anything to do with the composition of the oil.

But Figdor, with Environment Maine, insisted that the distinction is important because first responders and cleanup crews must know about the chemical composition of oil spills to respond correctly.

When the Enbridge pipeline in Michigan spilled millions of gallons of tar-sands oil in 2010, the company evaded questions about the precise origins of the product.

“It’s disappointing to see Exxon trying to pull the wool over people’s eyes,” Figdor said.

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